The present invention relates generally to a magnetically actuated detector which is responsive to proximation of a permeable object, and which is particularly useful in providing a magnetically actuated switch having unidirectional sensitivity to permeable objects.
Magnetic proximity switches employing reed switches or similar contact configurations for actuation in response to a magnetic field exist in the prior art. U.S. Pat. No. 5,128,641 provides a representative showing of a magnetic proximity switch wherein reed contacts are disposed in a neutral magnetic flux such that switch actuation occurs upon unbalancing the magnetic flux field. This type of magnetic proximity switch employs a plurality of magnets and places the reed switch axis in a magnetic field null position which is shifted or unbalanced by proximation of a permeable object to actuate the switch. This prior art magnetic switch does not have limited directional sensitivity, and therefore, cannot be mounted or located near a permeable material and remain actuatable with respect to proximation of a permeable target object.
Magnetic switches with reed type contacts that are actuatable in response to proximation of a permeable object, become permanently actuated when adjacently mounted to permeable material because the material creates a permanent change in the magnetic flux field. However, the embodiment of the present invention provides an apparatus which can be mounted on a permeable material and remain actuatable in response to a permeable target object.
Because magnetic proximity switches in the prior art are not unidirectional in sensitivity and are normally rendered inoperable when mounted on a permeable material there is a need for a simple, economical and effective unidirectional magnetic proximity detector; however, until now, no such apparatus has been developed.